904 - slipping reverse - any ideas?

[70 Charger RT]

My friend has a 75 Dart with a 318 / 904.  It clunks anytime he puts it in reverse (I think because of high idle).  The other day he put it in reverse and it didn't clunk like it usually does and after that it would slip in reverse.  It's not bad when it's cold but after about a minute of warming up, it would really slip and you can barely move the car.  The forward gears seem fine including 1st gear.  Oil looks clean and is not burnt and is right on the full mark.  Any ideas what his issue is?  Is it the front clutch seal? Is it the band ajustment? Any advice would be appreciated.
Thanks,
Randall
70 Charger RT

[John_Kunkel]

If 3rd gear is OK it's not likely a front clutch problem, more likely the rear band needs adjustment.

[70 Charger RT]

Thanks John, I'll give it a try.

[flyinlow]

Does it also slip warmed up in manual low?  As you slow (20mph) downshift into first, should have a firm low /reverse band apply. Proper low band adjust gives you engine braking in first.

Checking for a clean filter and excessive friction material in the pan would be in order.

[Challenger340]

904 Clunk going into reverse is "normal".

Valve Body "Bumps" the fluid Pressure when reverse selected, to overcome the added Resistence exerted on the Clutchs by forcing the Helical Cut Gears in the planetary backwards.

Bob

[70 Charger RT]

Thanks guys.